@@ -112,6 +112,14 @@ static void drop_current_rng(void)
}
/* Returns ERR_PTR(), NULL or refcounted hwrng */
+static struct hwrng *get_current_rng_nolock(void)
+{
+ if (current_rng)
+ kref_get(¤t_rng->ref);
+
+ return current_rng;
+}
+
static struct hwrng *get_current_rng(void)
{
struct hwrng *rng;
@@ -119,9 +127,7 @@ static struct hwrng *get_current_rng(void)
if (mutex_lock_interruptible(&rng_mutex))
return ERR_PTR(-ERESTARTSYS);
- rng = current_rng;
- if (rng)
- kref_get(&rng->ref);
+ rng = get_current_rng_nolock();
mutex_unlock(&rng_mutex);
return rng;
@@ -156,8 +162,6 @@ static int hwrng_init(struct hwrng *rng)
reinit_completion(&rng->cleanup_done);
skip_init:
- add_early_randomness(rng);
-
current_quality = rng->quality ? : default_quality;
if (current_quality > 1024)
current_quality = 1024;
@@ -321,12 +325,13 @@ static ssize_t hwrng_attr_current_store(struct device *dev,
const char *buf, size_t len)
{
int err = -ENODEV;
- struct hwrng *rng;
+ struct hwrng *rng, *old_rng, *new_rng;
err = mutex_lock_interruptible(&rng_mutex);
if (err)
return -ERESTARTSYS;
+ old_rng = current_rng;
if (sysfs_streq(buf, "")) {
err = enable_best_rng();
} else {
@@ -338,9 +343,15 @@ static ssize_t hwrng_attr_current_store(struct device *dev,
}
}
}
-
+ new_rng = get_current_rng_nolock();
mutex_unlock(&rng_mutex);
+ if (new_rng) {
+ if (new_rng != old_rng)
+ add_early_randomness(new_rng);
+ put_rng(new_rng);
+ }
+
return err ? : len;
}
@@ -460,13 +471,15 @@ static void start_khwrngd(void)
int hwrng_register(struct hwrng *rng)
{
int err = -EINVAL;
- struct hwrng *old_rng, *tmp;
+ struct hwrng *tmp;
struct list_head *rng_list_ptr;
+ bool is_new_current = false;
if (!rng->name || (!rng->data_read && !rng->read))
goto out;
mutex_lock(&rng_mutex);
+
/* Must not register two RNGs with the same name. */
err = -EEXIST;
list_for_each_entry(tmp, &rng_list, list) {
@@ -485,10 +498,8 @@ int hwrng_register(struct hwrng *rng)
}
list_add_tail(&rng->list, rng_list_ptr);
- old_rng = current_rng;
- err = 0;
- if (!old_rng ||
- (!cur_rng_set_by_user && rng->quality > old_rng->quality)) {
+ if (!current_rng ||
+ (!cur_rng_set_by_user && rng->quality > current_rng->quality)) {
/*
* Set new rng as current as the new rng source
* provides better entropy quality and was not
@@ -497,19 +508,26 @@ int hwrng_register(struct hwrng *rng)
err = set_current_rng(rng);
if (err)
goto out_unlock;
+ /* to use current_rng in add_early_randomness() we need
+ * to take a ref
+ */
+ is_new_current = true;
+ kref_get(&rng->ref);
}
-
- if (old_rng && !rng->init) {
+ mutex_unlock(&rng_mutex);
+ if (is_new_current || !rng->init) {
/*
* Use a new device's input to add some randomness to
* the system. If this rng device isn't going to be
* used right away, its init function hasn't been
- * called yet; so only use the randomness from devices
- * that don't need an init callback.
+ * called yet by set_current_rng(); so only use the
+ * randomness from devices that don't need an init callback
*/
add_early_randomness(rng);
}
-
+ if (is_new_current)
+ put_rng(rng);
+ return 0;
out_unlock:
mutex_unlock(&rng_mutex);
out:
@@ -519,10 +537,12 @@ EXPORT_SYMBOL_GPL(hwrng_register);
void hwrng_unregister(struct hwrng *rng)
{
+ struct hwrng *old_rng, *new_rng;
int err;
mutex_lock(&rng_mutex);
+ old_rng = current_rng;
list_del(&rng->list);
if (current_rng == rng) {
err = enable_best_rng();
@@ -532,6 +552,7 @@ void hwrng_unregister(struct hwrng *rng)
}
}
+ new_rng = get_current_rng_nolock();
if (list_empty(&rng_list)) {
mutex_unlock(&rng_mutex);
if (hwrng_fill)
@@ -539,6 +560,12 @@ void hwrng_unregister(struct hwrng *rng)
} else
mutex_unlock(&rng_mutex);
+ if (new_rng) {
+ if (old_rng != new_rng)
+ add_early_randomness(new_rng);
+ put_rng(new_rng);
+ }
+
wait_for_completion(&rng->cleanup_done);
}
EXPORT_SYMBOL_GPL(hwrng_unregister);
add_early_randomness() is called every time a new rng backend is added and every time it is set as the current rng provider. add_early_randomness() is called from functions locking rng_mutex, and if it hangs all the hw_random framework hangs: we can't read sysfs, add or remove a backend. This patch moves add_early_randomness() out of the rng_mutex zone. It only needs the reading_mutex. Signed-off-by: Laurent Vivier <lvivier@redhat.com> --- Notes: v2: in hwrng_register, take rng->ref only if rng is the new current_rng drivers/char/hw_random/core.c | 61 +++++++++++++++++++++++++---------- 1 file changed, 44 insertions(+), 17 deletions(-)